Method of conditioning wells



July 9, 1940. H. c. WHITE METHOD 0F CONDITIONING WELLS Filed sept. 29, 1957 In ve nio/1 Patented July 9, 1940 UNITED STATES PATENT OFFICE 2,207,184 i METHOD oF CONDITIONING WELLS Harry Calvin White, Los Angeles, Calif. y Application september' 29, 1937, serial No. 166,389

9 Claims.

This invention has to do generally with the art of conditioning oil wells with the view of increasing the ultimate production of a well by initially placing it, particularly the oil producing zone, in a condition such that later, when production has diminished below the potential` productivity of the well by reason of the accumulation of clogging bodies of any nature within the producing zone, that zone may again be opened in a simple operation to restore potential production.

First I place the producing region of the well in a condition favorable to maximum initial and continued production by insuring open porosity between the oil sands and the inlet or inlets through which the oil flows into the well pipe. For this purpose I may use a foraminate body of material comprising suitable size (for example gravel size) particles of shape and size most advantageous for the purpose, and which may be placed by any suitable method between the oil sands and the well pipe oil inlet or inlets. For example, the foraminate material may be placed within an underreamed and enlarged diameter portion ofthe well bore surrounding the usual perforated well pipe or liner, by any suitable method, as for instance that disclosed in Patent No. 2,083,625, issued June 15, 1937, to me on Method of depositing foraminate bodies around well casing. In this manner, I initially place the production zone between the oil sands and well pipe in a condition that will simulate and perhaps exceed the most favorable condition that .might exist in a natural formation. Y

The invention however is more particularly concerned with the function that the foraminate material shall later serve, after its interstitial spaceshave become clogged, when acted upon in the manner hereinafter explained. Briey, my

object is to predetermine the nature or composition of xthe foraminate material with relation to a treating agent, or type of agent, so that when later acted upon by that agent, the material will be affected, physically or chemically, to open the interstitial pores to such an extent that the clogging bodies will be removable by the natural ow from the formation, or by artificial flushing. Generally speaking, I aim to accomplish by the treatment of the foraminate material with the agent, a substantial reduction in the particle size and resultant increase in the size of the interstices. about by partial dissolution in or by the treatling agent, or by chemical reaction with the agent, in which there may occur afsimultaneous evolu- The reduction in particle size may comev (o1. 16s-2.1i)

tion of gas that will further aid in flushing the interstices.

As indicated, one of my major objects is to predetermine the composition of the foraminate material so that, contemplating future treatment of the material, the effect of the treating agent upon it will be known in advance. The placement of materials, such as gravel, around the perforated section of a well pipe is known in the art, but to my knowledge it has notbeen proposed, looking ahead to the future reconditioning of the well, to use a selected material that will be acted upon in a predetermined way by a predetermined type of treating agent. In this general connection it should be mentioned that common siliceous gravel, at least alone, is not suitable for my present process because of the extreme insolubility and chemical inertness o-f the gravel due to its .high content of silica or silica compounds, or the condition in which the silica is present. Moreover, I nd it advantageous to use different and preferably prepared materials because of the pos'- sibility of predetermining the shape of the particles to give greater interstitial openings and also to cause the material to be acted upon most effectively by the treating agent. It should be understood that I may use a silica containing material, such -as siliceous limestone, providing that material is capable off being affected in thedesired manner Yby the treating agent, but, as stated, the usual siliceous gravel heretofore proposed is not suitable for the reasons stated.

It is believed that the general class of mate' rials suitable for use as the foraminate oil passing medium will be understood from the foregoing, although certain typical examples'may be given as illustrative. I may use a suitable metal or metal alloy such as aluminum and aluminum alloys, formed in particles ofsuitable shape. Light weightmetals of this character may be particularly desirable when the material is to be deposited around a perforated pipe by upward movement in a stream of heavy fluid such as circulating mud. Particular metals may b e selected with relation to the well pipe metal with the view of avoiding or reducing any galvanic action that would bring about reduction or corro- `sion of any of the metals when an electrolytic condition exists in the well. Instead of metals, I may use substances or compounds such as the 50 alkaliearth carbonates, (e. g. calcium carbonate) which when acted upon by an acid reagent will result' in an evolution of gas. 'I'he particles advantageously may be made substantially spherical in form to providefor open porosity between the particles, desirable particle strength, and large surface exposure to the treating agent when the latter is introduced to the material.

The type of reagent to beemployed in the treatment of the material will of course depend upon the particle composition to the extent that the reagent will be capable of acting upon the particles to materially reduce their size. Thus, the reagent may be a solvent for the particles or it may be chemically reactive therewith; and when an acidic material is used the reagent may be alkaline, or acidic when the material is alkaline. Generally, acid reagents are preferred. As tothe specific materials referred to above, acid reagents such as aqueous solutions of hydrochloric, sulphuric or nitric acid, will react with the metals and will also react with the alkaline earth carbonates to liberate carbondioxide gas. Before or while treating the material with the reagent, the material may be treated with a suitable solvent such as a light petroleum fraction, toluene or the like, to dissolve asphaltic or waxy bodies that might interfere with the desired action of the reagent on the material. After a solvent treatment, the reagent may then be forced into the material under pressure, or circulated through-the material, until the action of the reagent is complete to the extent desired, which ordinarily will be when a substantial reduction in the particle size will have occurred. If necessary the reagent may then be flushed yout of the material.

The invention will perhaps be understood more fully and to better advantage by describing a typical and illustrative method of placing the foraminate material between the oil producing sands and the perforated portion of a well pipe or casing, bearing in mind however that the invention is not to be regarded as limited to any particular method of placing the material in the well. Throughout the description, reference is made to the accompanying drawing, in which:

Fig. 1 is a general view showing a typical casing string containing a charge of foraminate material;

Fig. 2 is a view similar to Fig. 1 showing the material placed about the perforated section of the casing;

Fig. 3 is a view similar to Fig. 2 showing the material deposited within an underreamed section of the well bore, with the casing cementedoff below the material;

Fig. 4 shows a string of tubing and plunger run into the well for the purpose of introducing a solution or reagent for the treatment of the foraminate material; and

Fig. 5 is a fragmentary enlarged view showing the preferred, substar ially spherical form of the foraminate material.

In Fig. 1, I show a typical string of casing I0 having at its upper end the usual head I I having fluid inlet I2 and outlet I3. At its lower end the casing carries the usual or any perforated section I4 at the upper end of which may be provided a suitable barrier, such as closely and circularly spaced bowed elements I5, that will permit upward circulation of fluid around the casing but which will arrest upward displacement of the deposited foraminate material. The material I6 to be deposited around the perforated section I4 of the casing may be introduced directly into the top of the casing in any suitable manner, either preceded by a plug I'I, or followed by a plug I8, or both. At the outset, the casing I0 may be raised off bottom so as to give ample clearance at the lower end of the perforated section for outward and upward displacement of material I6, and to provide any necessary space below the pipe to accommodate either or both of the plugs I'I and I8.

The material I6 is forced downwardly through the casing string and out the lower end of the perforated section I4 by pumping into the casing a column of circulating fluid 20. Plug I'I, if used, is forced out the lower end of the perforated section I4, permitting the subsequently discharged material I6 to be carried outwardly and upwardly to space 2| between the section I4 and the well bore wall 22 which, as previously indicated, extends through or within the oil sand or production zone. Pumping of fluid 20 into the casing is continued, causing the material I6 to be discharged from the perforated section I4, followed by plug I8, if used. While for the purpose of illustrating one method of operation I have shown both plugs in Fig. 1, for the purposes of Fig. 2 it may be assumed that only the upper plug I8 is used and that the density of the material I6 with relation to the specific gravity of the circulating fluid, which of course may be controlled by the addition of mud, is such that the material will be substantially floated in the fluid.

By continued operation of the circulating fluid pumps, the fluid is caused to circulate upwardly through space 24 around the casing to the ground surface, and a suiliciently high fluid velocity is maintained to effectively aid in carrying or floating the particles of the material I6 upwardly to the barrier I5, so that the material may substantially fill the space 2| around the perforations I4a. Where the material I6 consists of light weight particles, or any weight par- `v ticles that do not substantially exceed in density the specific gravity of the circulating fluid, the particles will be floated upwardly into place about the perforations. For the purpose of compacting the particles in the mass I6, the casing string may be vertically reciprocated during the process of placing the material. Thereafter, the casing may be set down on the bottom of the hole (the plug may be removed or drilled through if necessary), or the lower portion of section I6 cemented-off below the perforations.

As illustrated in Fig. 5, the individual particles I6a preferably will be made substantially spherical in form and of such size as to provide open porosity through the interstitial spaces 25 between the particles. The bed of material I6 thus initially provides a foraminate medium through which the oil may readily pass from the formation into the perforations I4a.

Fig. 3 shows the foraminate material deposited as described above, within an underreamed and enlarged diameter section 26 of the well bore containing the perforated section of the casing. Here the shoulder 21 formed by the underreaming operation presents a barrier against upward.

displacement of the foraminate material beyond the underreamed section of the hole. Sufficient material I6 may be introduced to completely fill bore 26 from the lower end of the perforated casing section I6, and the casing then set on bottom as indicated by the dot-dash lines in Fig. 3, or the lower portion of section I6 below the perforations may be cemented-off as indicated at 28.

Assuming the well, initially conditioned as described above, to have been put on production and eventually the interstitial spaces 25 between the particles 16a to have become clogged to the extent of seriously diminishing the productive capacity of the well, the material I6 may then be treated with reagent by any suitable method to open the interstices in the manner previously discussed. To illustrate, I may lower within the casing a string of tubing 29 carrying at its lower end a plunger 30, through the central passage 3| of which uid may be discharged within the perforated section of the casing past check valve 32. I may rst pump down through the tubing 29 a suitable solvent that will be discharged downwardly into the interior of the perforated section I4, and outwardly against and through the perforations into the material I6 by way of passages 33 communicating with an annular groove 34 in the plunger. By reciprocating .the plunger through the length of the perforated area or the casing. and at the same time discharging the 4 solvent under pressure through the perforations, I may first flush the foraminate bed I6 to dissolve asphaltic or paralnic bodies that might interfere with the action upon material by the subsequently introduced reagent.

As previously explained, the material composition and type of reagent Will have been predetermined to insure that when introduced to the well, the reagent will have the desired action upon the particles |6a of the material. After the solvent treatment, the reagent may be introduced through the pipe string 29 and discharged under pressure outwardly through the casing perforations intothe material I6, in the same manner described with reference to the solvent treatment. In this manner the reagent is caused to thoroughly permeate the bed of material I6 and to attack the particles Ilia, reducing their sizes and opening up the interstitial spaces 25. The solvent and reagent Will also act upon and penetrate the production sands in the bore wall 26, thus opening the formation interstices as well as the spaces between the particles lSa. As will be understood, the reagent may be introduced to the material I6 in quantity and over a period of time necessary to cause a reduction of the particle size to an extent that will restore the desired open communication between the production sands and the casing perforations Ida.

After treatment by the reagent, the material I6 may be flushed out by Water or other suitable flushing fluid if necessary, although ordinarily the restored natural flow from the formation will sulce to remove the reagent and any desirable reaction products resulting from the action of the reagent on the material.

1. The method that includes, placing at the outside of an apertured well pipe a foraminate body of Well fluid passing material attackable by a iluid reagent to open interstitial spaces within said material, and later, when such spaces have become clogged, introducing said reagent to the Well to attack said material and open its interstitial spaces.

2. The method that includes, placing at the outside of an apertured Well pipe a foraminate body of well uid passing material, attackable by an acid reagent of the group consisting of hydrochloric, sulfuric and nitric acids, to open interstitial spaces within said material, and later, when such spaces have become clogged, intro- .ducing an acid of said group to the Well to attack said material and open its interstitial spaces.

3. In the Well conditioning art in which there has been placed at the outside of an apertured well pipe a porous body of well uid passing material comprising particles attackable by a uid reagent to open the pores of the material; the method of restoring the porosity of said material when it becomes clogged with sand, that includes treating said material with said reagent introduced to the well and thereby reducing the size of said particles to open clogged interstitial spaces between them.

4. In the well conditioning art in which there has been placed at the outside of an apertured well pipe a foraminate body of well uid passing material including particles chemically attackable'by an acid reagent of the group consisting of hydrochloric, sulfuric and nitric acids; the method that includes, treating said material with an acid reagent of said group and by virtue of the resultant chemical reaction opening clogged interstitial spaces between said particles.

5. In the well conditioning art in which there has been placed at the outside of an apertured well pipe a foraminate body of well fluid passing material including particles attackable by an acid reagent o f the group consisting of hydrochloric, sulfuric and nitric acids; the method that includes, treating said material with an acid reagent of said group by forcing the acid out through the pipe perforations into said material and thereby reducing the size of said particles to open clogged interstitial spaces between them.

6. The method that includes, placing at the outside of an apertured well pipe a foraminate body of Well iluid passing material containing an alkaline earth metal carbonate attackable by an acid reagent to open interstitial spaces Within saidmaterial, and later, when such spaces have become clogged, introducing said acid to the well to attack said material and open its interstitial spaces.

7.7The method that includes, placing at the outside of an apertured well pipe a foraminate body of IWell uid passing medium comprising silica and a soluble material attackable by a uid reagent to open interstitial spaces within said medium, and later, when such spaces have become clogged, introducing said reagent to the well to attack said soluble material and open said interstitial spaces.

8. A foraminate pack for wells comprising a porous body of material comprising silica and a solid soluble substance, said soluble substance being adapted to be dissolved to open interstitial spaces in said body after such spaces have become clogged.

9. A foraminate pack for Wells comprising a porous body of material comprising silica and an alkaline earth metal carbonate, said carbonate being adapted to be dissolved to open interstitial spaces in said body after such spaces have become clogged.

HARRY CALVIN WHITE. 

